Epidemiology of ROP in the Stockholm area of Sweden

A prospective, population-based study of the epidemiology of ROP in a well-defined geographical area of Sweden was performed. Two hundred and sixty children with a birth weight of 1500 g or less, and surviving for at least eight weeks, were included in the study. ROP was seen in 40.4% of the children. We suggest that prematurely born children with a gestational age of 32 weeks or less ought to be screened for ROP.

Background light adaptation of the retinal neuronal adaptive system. I. Effect of background light intensity

The behaviour of the neuronal adaptive retinal mechanisms to environmental light exposures was studied by measuring the oscillatory potentials (OPs) of the electroretinogram. Dark adapted rats were exposed to four levels of background light (BG), starting at a 'low scotopic' level of 1.43x 10(6) cd/m2, increased by steps of two log units, through 'high scotopic' -, 'low mesopic' - and finally the 'high mesopic' BG of 1.43x 10(0) cd/m2. The summed oscillatory response significantly increased as the BG intensity was raised, except at the 'high mesopic' level. The amplitudes of the a- and b-waves reduced as the BG light increased above the 'high scotopic' level. Each OP responded individually to the different BGs. O1 and O2, significantly enhanced at the 'low scotopic' BG. The amplitudes of the three later OPs increased significantly at the 'low mesopic' BG. The adaptational behaviour of the retinal oscillatory response to BG illumination was different to that of the a- and b- waves. The results indicate that the adaptational neuronal system, as reflected by the OPs, seems to be relatively robust and is separate from the slower photochemical adaptive process in the distal retina. The tentative corollary suggests the oscillatory system to play a vision-preserving role, possibly as an alert against undue depletion of the slowly regenerating visual pigment. The enhancement of the oscillatory response at the 'mesopic' illumination levels indicate both scotopic and photopic processes to contribute to neuronal adaptive activity of the retina.

Ophthalmological follow up of preterm infants: a population based, prospective study of visual acuity and strabismus

BACKGROUND/AIMS

Prematurely born infants are known to have an increased rate of ophthalmological morbidity. The aim of the present study was to investigate visual acuity and ocular alignment in a population of preterm infants in a geographical area, in infants with and without retinopathy of prematurity (ROP).

METHODS

A prospective population based study of ophthalmological status of preterm infants with a birth weight of 1500 g or less was performed during 3.5 years, with examinations at 6, 18, 30, and 42 months of corrected age. Visual acuity was tested using linear optotypes. Multiple regression analyses were used to analyse independent risk factors for poor vision and strabismus.

RESULTS

Poor vision (< 0.3) was detected in 2.5% (6/237) of the children. Of these, only two (0.8%) had a severe visual impairment (< 0.1). Strabismus occurred in 13.5% (31/229). Children with cryotreated ROP and neurological complications ran the highest risk of poor vision and strabismus, according to multiple regression analysis. Among children without a history of ROP or neurological complications, 34% had a visual acuity < 0.7 and 5.9% had strabismus, compared with 61% and 22%, respectively, among the children with ROP or neurological complications.

CONCLUSIONS

The overall incidence of subnormal vision and strabismus in children born prematurely was higher than in a full term population of the same age. On the basis of this study, follow up of all preterm infants screened for ROP is recommended and general guidelines are suggested.

Ophthalmological long-term follow up of preterm infants: a population based, prospective study of the refraction and its development

BACKGROUND

Numerous studies have reported an increased risk of refractive errors in prematurely born infants, but only few have been long-term and strictly population based.

METHODS

A 3.5 year ophthalmological long term follow up of 248 preterm infants was performed. The infants had been included in a previous epidemiological study of retinopathy of prematurity (ROP) (birth weight < or = 1500 grams). The incidence of refractive errors and development of refraction were studied, based on retinoscopies at 6 and 30 months of corrected age.

RESULTS

The overall incidence of myopia was 8% at 6 months, of which 35% was transient, and 10% at 30 months. Of the cryotreated infants, 30-40% were myopic at both retinoscopies. The incidence of astigmatism was 52% at 6 months and 26% at 30 months. Astigmatism was associated with ROP, but not with cryotreated ROP itself. Astigmatism "against the rule" was commoner than astigmatism "with the rule". Anisometropia occurred in 6.5% of the infants at 6 months and in 8.4% at 30 months. The incidence of anisometropia was higher in eyes with ROP, particularly in cryotreated eyes, which tended to have high and persistent anisometropia.

CONCLUSION

The risk of refractive errors is higher in preterm infants than in infants born at term, and also prematurely born infants without ROP do run an increased risk of having myopia and anisometropia. We recommend follow up examinations with retinoscopy for all infants included in screening programmes for ROP.

Cataract development in adult bone marrow transplant recipients

In a prospective study, adult patients treated with bone marrow transplantation were examined with respect to cataract development. There were 99 patients with a survival of at least one year. Ten of them had aplastic anemia and the rest had various hematological malignancies. Mean follow-up time was 3.9 years (range 1-10). All in the hematological malignancies group but none in the aplastic anemia group, were conditioned with irradiation. Cytostatic drugs were administered in all cases. Depending on the type of disease and its reaction to bone marrow transplantation, steroid treatment was sometimes indicated. Cataract did not occur in any of the 10 patients treated for aplastic anemia, whereas all patients with hematological malignancies had developed cataract after 4 years' observation. Most patients in the hematological malignancies group already showed lens opacifications after 2 years. Cataract surgery on the first eye was performed in 39 cases, a median of 3.7 years after bone marrow transplantation. Cataract development was clearly correlated to radiation. No relationship was found to other conditioning treatments, although a synergistic effect is possible.

A population based, prospective study of the development of ROP in prematurely born children in the Stockholm area of Sweden

A prospective population based study including 260 children with a birth weight of 1500 g or less was performed in the Stockholm county. The total incidence of retinopathy of prematurity (ROP) was 40.4%, while severe ROP--that is, stage 3 or more, was seen in 20.0%. Cryotherapy was performed in 10.8%. Logistic regression analysis revealed independent association of both gestational age and birth weight with ROP. The association of gestational age and ROP was significantly stronger, indicating that the degree of immaturity of the eye is a main predictive factor for the development of ROP. The purpose of a general screening for ROP is to identify children requiring cryotherapy. Based on these results it seems appropriate to include children with a gestational age of 32 weeks or less in such a programme and a first examination at 5-6 weeks of postnatal age is suggested.

The postnatal development of the oscillatory potentials of the electroretinogram V. Relation to the double peaked a-wave

The postnatal development of the double peaked a-wave and its relation to the oscillatory potentials of the rat electroretinogram was studied. The split a-wave appeared one day later than the first oscillatory activity. The appearance and maturation of the positivity between the two a-waves (a-hump) was found to be similar to that of the first oscillatory potential, and the development of the second a-wave showed similarities to that of the second oscillatory potential. Thus, we conclude that the double peaked a-wave is closely related to the appearance of the two first oscillatory potential. Secondly, the division of the a-wave in the immature animal may be caused by the intrusion of the first oscillatory potential. Thirdly, the presence of a split a-wave before spontaneous opening of the lid seems to indicate a state of comparatively progressed maturity of neuronal adaptation.

The postnatal development of the oscillatory potentials of the electroretinogram. IV. Mesopic characteristics

The postnatal development of the oscillatory potentials (OP) of the rat's electroretinogram (ERG) was studied during relatively mesopic adaptational conditions. The behaviour of the OPs induced at an interstimulus interval (ISI) of 30 sec entailed photopic qualities at an individual level, but when summated conformed to a scotopic course of postnatal maturation. An ISI of 1 min elicited OPs with individual scotopic characteristics. The total oscillatory activity culminated at 17 days of age at both ISIs, similar to more scotopically induced oscillations. These results show that relatively mesopic states of adaptation do not promote any earlier appearance of the OPs, and that the immature mesopically induced OPs seem to contain both scotopic and photopic qualities reflecting a postnatal change of balance between these components. Furthermore, photopic mechanisms seem to govern the oscillatory activity in the mature rat retina. We suggest that the differences in relation to adaptational conditions between the immature and mature OPs may reflect the postnatal status of the dopamine and its synthetizing enzyme, tyrosine-hydroxylase.

The postnatal development of the oscillatory potentials of the electroretinogram. III. Scotopic characteristics

The postnatal development of the oscillatory potentials (OPs) of the rat electroretinogram (ERG) was studied during more extreme scotopic conditions. Enhancement of scotopic conditions did not facilitate any earlier appearance of the OPs, including the later ones, compared to previously studied less scotopic conditions. The oscillatory activity appeared at Days 12 to 15, and increased rapidly up to Day 17, which coincided with the major period of development of the photoreceptors. After the physiological opening of the eyelids there was a decline of the OPs. We propose that the decline of the oscillatory activity induced during more extreme scotopic conditions is related to early cell death in the distal retina and/or to developmental neuronal plasticity in the proximal retina.

Intrathecal antibody production against viruses of the herpesvirus family in acute retinal necrosis syndrome

Viruses of the herpesvirus family cause acute retinal necrosis syndrome, a devastating necrotic retinitis in immunocompetent individuals. Direct proof of the viral origin of this disease may be obtained by demonstration of the virus, viral antigens, or viral DNA in biopsy specimens of retinas. In search of alternative diagnostic methods, we analyzed cerebrospinal fluid and serum with enzyme-linked immunosorbent assays for virus-specific antibody activity. Intrathecally produced viral antibodies were found in three consecutive patients with acute retinal necrosis syndrome: herpes simplex type 2 in a 30-year-old woman with a history of suspected neonatal herpes encephalitis, herpes simplex type 1 in a 35-year-old man, and varicella-zoster virus activity in a 62-year-old woman. None of the patients had clinical signs indicating an acute disorder in the central nervous system. This serologic approach seems to be of value for the diagnosis of an associated intracerebral viral infection in cases of acute retinal necrosis syndrome.

The development of cataract in children as a late side-effect of bone marrow transplantation

Children with hematological malignancies (n = 33), severe aplastic anemia (SAA, n = 7) and other non-malignant diseases (n = 4) were followed for cataract development after bone marrow transplantation (BMT). The children with hematological malignancies were subjected to total body irradiation (TBI), 10 Gy, in one session with no shielding of the eyes as part of their conditioning regimen before BMT. The children with SAA or other non-malignant diseases received either no irradiation before BMT or a reduced dose, 8 Gy, with shielding of their eyes. After 3 years all patients who had undergone BMT for hematological malignancies had developed lens opacification. No patients in the other groups, without leukemia, showed any sign of cataract development. There was no relationship between steroid treatment for graft-versus-host disease and cataract development. No relation to age of onset of treatment or to the sex of the patient and cataract formation was seen. It seems evident from the present study that TBI given in one session was the main cause of cataract development after BMT.

The postnatal development of the oscillatory potentials of the electroretinogram. II. Photopic characteristics

The postnatal development of the oscillatory potentials (OPs) of the rat's electroretinogram (ERG) was studied during more extreme photopic conditions. The appearance of the OPs was further delayed, by 1 to 3 days, compared to previously studied less photopic conditions. A rapid phase of development of the total OP activity occurred at the age of 15 days, which coincided with the physiological opening of the eye-lids. During maturation the first two OPs were enhanced while the later OPs were attenuated. The total OP activity culminated at the age of 30 days. These results strongly indicate that the rapid neuronal adaptive system appears and develops later than the slow photochemical one. Secondly, the fast phase of maturation of the neuronal adaptive process, as reflected in the OPs, seems to be dependent on environmental light. Thirdly, the findings support previous indications that two different systems seem to be responsible for the OPs in the rat and thus the earlier OPs to have different origins from those of the later ones.

A follow-up study of children with neonatal herpes simplex virus infections with particular regard to late nervous disturbances

Forty-five children with neonatal herpes simplex virus (HSV) infection, representing all known cases in the diagnostic records of four virological laboratories within a 15-year period, were followed up. Twelve children had died. Sixteen of the 33 survivors were healthy. Thirteen children had severe disabilities: all of them showed severe mental retardation; moreover, 11 were tetraplegic, one was hemiplegic with hydrocephalus and one had a pronounced behavioural abnormality. Four children had slight to moderate disabilities: one child was mildly mentally retarded and three, although mentally normal, had hemiplegia and delayed speech development, one of them having a learning disorder as well. Of these 17 neurologically impaired children 16 had ophthalmological abnormalities. EEG recordings were made in 29 patients in the neonatal period. They were markedly abnormal in 24 patients, 14 of whom had localized periodic complexes. An abnormal EEG was a bad prognostic sign. The neurological outcome was better in the HSV-1-infected children (10 cases) than in the HSV-2-infected ones (35 cases). Progressive or recurrent encephalitis was strongly suspected in two preterm children.

Late ophthalmologic manifestations of neonatal herpes simplex virus infection

We examined 32 children one to 15 years after virologically verified neonatal herpes simplex virus infection. Sixteen of 17 (94%) neurologically impaired children had ocular abnormalities compared to three of 15 (20%) neurologically healthy children. Disturbed oculomotor control occurred in 14 children (44%), most of whom were among those with severe handicap. Ocular morbidity was present in 13 (40%) of 32 children: one had cataracts, two had corneal scars, seven had optic atrophy, and nine had chorioretinal scars. The clinically silent chorioretinal lesions were manifest as coarse hyperpigmented areas between the equator and ora serrata. One child had suffered from acute fulminant retinitis. Twelve of 13 (93%) severely handicapped children had impaired vision, mainly because of cortical blindness. Less affected children had normal vision unless corneal scars were present. Long-term observation of patients with neonatal herpes infections is essential because ocular manifestations are not rare, and recurrences may be more common than previously reported.

Dry eye syndrome in long-term follow-up of bone marrow transplanted patients

Out of 77 bone marrow transplanted patients surviving at least 1 year, 43% developed ocular manifestations of the sicca syndrome. This reaction was more frequent in patients with graft-versus-host disease (GVHD). Kerato-conjunctivitis sicca (KCS) developed in 28 patients (54%) who had survived acute GVHD but in only five cases (20%) of those without that complication. The incidence of dry eyes was 62% in the chronic GVHD group. All seven sicca cases in patients with aplastic anemia were seen in patients with chronic GVHD, while 10 out of 26 patients with hematological malignancies and without chronic GVHD had KCS. Two of these had not experienced any acute GVHD. Irradiation may contribute to the development of KCS, since all patients with hematological malignancies, in contrast to aplastic anemia patients, had undergone total body irradiation.

The effect of postnatal exposure to lead on the electroretinogram in young rats

The morphological and electrophysiological effects on the retina resulting from lead exposure were assessed in neonatal rats. The electroretinogram (ERG), light and electron microscopy and morphometry of the retina were evaluated at 9, 11 and 13 days of age. The lead concentration in the blood was on average between 276 and 311 micrograms/100 ml in the different age groups. The brain concentration of lead varied on average between 102 and 104 micrograms/100 g. A reduction in amplitude, a prolonged latency and an elevated threshold sensitivity of the a-wave was observed in the 11 days old lead-exposed pups. The 13 days old lead-fed rats showed depressed amplitudes and delayed peak times of both the a- and b-waves. The latency of the a-wave was also longer in the lead-treated 13 days old animals. No ERG was recorded at the age of 9 days in neither the lead-exposed or control animals. No significant change in the morphology of the retina was found. We propose that lead exposure seem to induce a change primarily in the electrophysiological function of the photoreceptors. There was no evidence for a direct retardation of the development of the retina by the administration of lead.

Effects of manganese chloride on the rat developing nervous system

Sprague-Dawley rats were exposed to sublethal doses of manganese chloride during their postnatal development period up to 44 days of age. They showed transient clinical signs of disease and a decreased homovanillic acid (HVA) content in the striatum and hypothalamus between 15 and 22 days of age. The manganese content in the brain was increased 20-40 times during this period as determined with neutron activation analyses. In spite of this no structural damage or signs of maturation disturbances in the nervous system were found. Interruption of manganese exposure reversed the changes in HVA content.

Studies on developmental alterations in the electroretinogram in rats after post-natal exposure to lead

The effects of post-natal exposure to lead on the development of the electroretinogram in rats were studied. Newborn rats were fed with lead acetate by gastric intubation and weight and age-matched control rats were given sodium acetate in a similar way. At 15 and 26 days of age the lead concentrations in blood were on average 298 micrograms/100 ml and 80 micrograms/100 ml, respectively. The brain concentrations of lead were on average 248 micrograms/100 mg in the 15-day-old lead-fed animals and 244 micrograms/100 mg in the 26-day-old ones. Lead produced a transient depression of the post-natal development of the electroretinogram. A decrease in the amplitudes of the a- and b-waves, as well as an increase in the peak times of these potentials were found in the 15-day-old animals. The ERGs of the 26-day-old animals did not differ from controls. There were no morphological changes of the retina.

Oscillatory potentials of the electroretinogram in patients with unilateral optic atrophy

The oscillatory potentials (OP) of the electroretinogram (ERG) of 26 patients with unilateral optic atrophy were studied. The severity of optic atrophy was graded according to clinical findings. Three groups of increasing interocular difference in contrast sensitivity and changes of the visual evoked cortical potentials were obtained. No significant difference between the amplitudes or peak latencies of the individual oscillatory peaks or summed amplitudes of the OPs between the affected and control fellows eyes in any group was found. Neither was there any significant interocular differences regarding the a- and b-waves. These findings show that there does not seem to be any major contribution of ganglion cell activity in the generation of the OPs. Secondly, the results do not support the existence of centrifugal optic nerve innervation of the human retina.